LibJS: Fix logical expressions

The current implementation of logical AND (&&) and logical OR (||)
always returns a boolean - this is not correct.

Libraries/LibJS/AST.cpp

@@ -279,17 +279,21 @@ Value BinaryExpression::execute(Interpreter& interpreter) const
 
 Value LogicalExpression::execute(Interpreter& interpreter) const
 {
-    auto lhs_result = m_lhs->execute(interpreter).to_boolean();
+    auto lhs_result = m_lhs->execute(interpreter);
     if (interpreter.exception())
         return {};
-    auto rhs_result = m_rhs->execute(interpreter).to_boolean();
+    auto rhs_result = m_rhs->execute(interpreter);
     if (interpreter.exception())
         return {};
     switch (m_op) {
     case LogicalOp::And:
-        return Value(lhs_result && rhs_result);
+        if (lhs_result.to_boolean())
+            return Value(rhs_result);
+        return Value(lhs_result);
     case LogicalOp::Or:
-        return Value(lhs_result || rhs_result);
+        if (lhs_result.to_boolean())
+            return Value(lhs_result);
+        return Value(rhs_result);
     }
 
     ASSERT_NOT_REACHED();

Libraries/LibJS/Parser.cpp

@@ -889,7 +889,9 @@ bool Parser::match_secondary_expression() const
         || type == TokenType::QuestionMark
         || type == TokenType::Ampersand
         || type == TokenType::Pipe
-        || type == TokenType::Caret;
+        || type == TokenType::Caret
+        || type == TokenType::DoubleAmpersand
+        || type == TokenType::DoublePipe;
 }
 
 bool Parser::match_statement() const

Libraries/LibJS/Tests/logical-expressions-basic.js

@@ -0,0 +1,83 @@
+function assert(x) { if (!x) throw 1; }
+
+try {
+    assert((true && true) === true);
+    assert((false && false) === false);
+    assert((true && false) === false);
+    assert((false && true) === false);
+    assert((false && (1 === 2)) === false);
+    assert((true && (1 === 2)) === false);
+    assert(("" && "") === "");
+    assert(("" && false) === "");
+    assert(("" && true) === "");
+    assert((false && "") === false);
+    assert((true && "") === "");
+    assert(("foo" && "bar") === "bar");
+    assert(("foo" && false) === false);
+    assert(("foo" && true) === true);
+    assert((false && "bar") === false);
+    assert((true && "bar") === "bar");
+    assert((null && true) === null);
+    assert((0 && false) === 0);
+    assert((0 && true) === 0);
+    assert((42 && false) === false);
+    assert((42 && true) === true);
+    assert((false && 0) === false);
+    assert((true && 0) === 0);
+    assert((false && 42) === false);
+    assert((true && 42) === 42);
+    assert(([] && false) === false);
+    assert(([] && true) === true);
+    assert((false && []) === false);
+    assert((true && []).length === 0);
+    assert((null && false) === null);
+    assert((null && true) === null);
+    assert((false && null) === false);
+    assert((true && null) === null);
+    assert((undefined && false) === undefined);
+    assert((undefined && true) === undefined);
+    assert((false && undefined) === false);
+    assert((true && undefined) === undefined);
+
+    assert((true || true) === true);
+    assert((false || false) === false);
+    assert((true || false) === true);
+    assert((false || true) === true);
+    assert((false || (1 === 2)) === false);
+    assert((true || (1 === 2)) === true);
+    assert(("" || "") === "");
+    assert(("" || false) === false);
+    assert(("" || true) === true);
+    assert((false || "") === "");
+    assert((true || "") === true);
+    assert(("foo" || "bar") === "foo");
+    assert(("foo" || false) === "foo");
+    assert(("foo" || true) === "foo");
+    assert((false || "bar") === "bar");
+    assert((true || "bar") === true);
+    assert((null || true) === true);
+    assert((0 || false) === false);
+    assert((0 || true) === true);
+    assert((42 || false) === 42);
+    assert((42 || true) === 42);
+    assert((false || 0) === 0);
+    assert((true || 0) === true);
+    assert((false || 42) === 42);
+    assert((true || 42) === true);
+    assert(([] || false).length === 0);
+    assert(([] || true).length === 0);
+    assert((false || []).length === 0);
+    assert((true || []) === true);
+    assert((null || false) === false);
+    assert((null || true) === true);
+    assert((false || null) === null);
+    assert((true || null) === true);
+    assert((undefined || false) === false);
+    assert((undefined || true) === true);
+    assert((false || undefined) === undefined);
+    assert((true || undefined) === true);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}